Hence the mistakes in our thinking, the errors in judgment, the thousand inconsistencies and self-deceptions. But the mind can do otherwise, can defend itself from interruptions and extraneous influences by making use of its freedom and of its power to follow its own laws and no others. It is thus possible for us to have not only psychical experiences but knowledge; only in this way can truth be reached, and error rejected. Thus science can follow a sure course. Thus alone, for instance, could the great edifice of geometry and arithmetic have been built up in its indestructible certainty. The progress from axiom to theorem and to all that follows is due to free thought, obeying the laws of inference and demonstration, and entirely unconcerned about the laws of association or the natural laws of the nervous agitations, the electric currents, and other plays of energy which may go on in the brain at the same time. What have the laws of the syllogism to do with the temporary states of tension in the brain, which, if they had free course, would probably follow lines very different from those of Euclid, and if they chanced once in a way to follow the right lines from among the millions of possibilities, would certainly soon turn to different ones, and could never examine them to see whether they were right or not. Thus it is not any highly aspiring emotional desire or any premature prejudice, but the solid old science of logic that first and most determinedly shuts the door in face of the claims of naturalism. If we combine this with what has already been said on page 154, we shall see how dangerous it would be for naturalism to be proved right in the dispute; for then it would be wholly wrong. For, as it is only through the free, thinking mind that true and false can be distinguished and brought into relation with things, so only through it can we have an ideal of truth to be recognised and striven after, and that spontaneous, pertinacious, searching, following, and discovering which constitutes science as a whole and in detail. And in so far as naturalism itself claims to be nothing more than an attempt towards this goal, it is itself only possible on the basis of something which it denies.